reselect/website/docs/api/createStructuredSelector.mdx

---
id: createStructuredSelector
title: createStructuredSelector
sidebar_label: createStructuredSelector
hide_title: true
description: 'createStructuredSelector'
---

import Tabs from '@theme/Tabs'
import TabItem from '@theme/TabItem'
import { InternalLinks } from '@site/src/components/InternalLinks'

# `createStructuredSelector`

A convenience function that simplifies returning an object made up of selector results.

## Parameters

| Name                   | Description                                                                          |
| :--------------------- | :----------------------------------------------------------------------------------- |
| `inputSelectorsObject` | A key value pair consisting of input selectors.                                      |
| `selectorCreator?`     | A custom selector creator function. It defaults to <InternalLinks.CreateSelector />. |

## Returns

A memoized structured selector.

## Type Parameters

| Name                   | Description                                                                                                                                               |
| :--------------------- | :-------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `InputSelectorsObject` | The shape of the <InternalLinks.InputSelectors /> object.                                                                                                 |
| `MemoizeFunction`      | The type of the memoize function that is used to create the structured selector. It defaults to `lruMemoize`.                                             |
| `ArgsMemoizeFunction`  | The type of the of the memoize function that is used to memoize the arguments passed into the generated structured selector. It defaults to `lruMemoize`. |

## Examples

### Modern Use Case

{/* START: createStructuredSelector/modernUseCase.ts */}

<Tabs
  groupId='language'
  defaultValue='ts'
  values={[
    {label: 'TypeScript', value: 'ts'},
    {label: 'JavaScript', value: 'js'},
  ]}>
  <TabItem value='ts'>

```ts title="createStructuredSelector/modernUseCase.ts"
import { createSelector, createStructuredSelector } from 'reselect'

export interface RootState {
  todos: {
    id: number
    completed: boolean
    title: string
    description: string
  }[]
  alerts: { id: number; read: boolean }[]
}

// This:
export const structuredSelector = createStructuredSelector(
  {
    todos: (state: RootState) => state.todos,
    alerts: (state: RootState) => state.alerts,
    todoById: (state: RootState, id: number) => state.todos[id]
  },
  createSelector
)

// Is essentially the same as this:
export const selector = createSelector(
  [
    (state: RootState) => state.todos,
    (state: RootState) => state.alerts,
    (state: RootState, id: number) => state.todos[id]
  ],
  (todos, alerts, todoById) => {
    return {
      todos,
      alerts,
      todoById
    }
  }
)
```

  </TabItem>
  <TabItem value='js'>

```js title="createStructuredSelector/modernUseCase.js"
import { createSelector, createStructuredSelector } from 'reselect'

// This:
export const structuredSelector = createStructuredSelector(
  {
    todos: state => state.todos,
    alerts: state => state.alerts,
    todoById: (state, id) => state.todos[id]
  },
  createSelector
)

// Is essentially the same as this:
export const selector = createSelector(
  [state => state.todos, state => state.alerts, (state, id) => state.todos[id]],
  (todos, alerts, todoById) => {
    return {
      todos,
      alerts,
      todoById
    }
  }
)
```

  </TabItem>
</Tabs>

{/* END: createStructuredSelector/modernUseCase.ts */}

In your component:

{/* START: createStructuredSelector/MyComponent.tsx */}

<Tabs
  groupId='language'
  defaultValue='tsx'
  values={[
    {label: 'TypeScript', value: 'tsx'},
    {label: 'JavaScript', value: 'jsx'},
  ]}>
  <TabItem value='tsx'>

```tsx title="createStructuredSelector/MyComponent.tsx"
import type { RootState } from 'createStructuredSelector/modernUseCase'
import { structuredSelector } from 'createStructuredSelector/modernUseCase'
import type { FC } from 'react'
import { useSelector } from 'react-redux'

interface Props {
  id: number
}

const MyComponent: FC<Props> = ({ id }) => {
  const { todos, alerts, todoById } = useSelector((state: RootState) =>
    structuredSelector(state, id)
  )

  return (
    <div>
      Next to do is:
      <h2>{todoById.title}</h2>
      <p>Description: {todoById.description}</p>
      <ul>
        <h3>All other to dos:</h3>
        {todos.map(todo => (
          <li key={todo.id}>{todo.title}</li>
        ))}
      </ul>
    </div>
  )
}
```

  </TabItem>
  <TabItem value='jsx'>

```jsx title="createStructuredSelector/MyComponent.jsx"
import { structuredSelector } from 'createStructuredSelector/modernUseCase'
import { useSelector } from 'react-redux'

const MyComponent = ({ id }) => {
  const { todos, alerts, todoById } = useSelector(state =>
    structuredSelector(state, id)
  )

  return (
    <div>
      Next to do is:
      <h2>{todoById.title}</h2>
      <p>Description: {todoById.description}</p>
      <ul>
        <h3>All other to dos:</h3>
        {todos.map(todo => (
          <li key={todo.id}>{todo.title}</li>
        ))}
      </ul>
    </div>
  )
}
```

  </TabItem>
</Tabs>

{/* END: createStructuredSelector/MyComponent.tsx */}

### Simple Use Case

```ts
const selectA = state => state.a
const selectB = state => state.b

// The result function in the following selector
// is simply building an object from the input selectors
const structuredSelector = createSelector(selectA, selectB, (a, b) => ({
  a,
  b
}))

const result = structuredSelector({ a: 1, b: 2 }) // will produce { x: 1, y: 2 }
```

`createStructuredSelector` takes an object whose properties are input selectors and returns a structured selector. The structured selector returns an object with the same keys as the `inputSelectorsObject` argument, but with the selectors replaced with their values.

```ts
const selectA = state => state.a
const selectB = state => state.b

const structuredSelector = createStructuredSelector({
  x: selectA,
  y: selectB
})

const result = structuredSelector({ a: 1, b: 2 }) // will produce { x: 1, y: 2 }
```

Structured selectors can be nested:

```ts
const nestedSelector = createStructuredSelector({
  subA: createStructuredSelector({
    selectorA,
    selectorB
  }),
  subB: createStructuredSelector({
    selectorC,
    selectorD
  })
})
```

## Defining a Pre-Typed <InternalLinks.CreateStructuredSelector>`createStructuredSelector`</InternalLinks.CreateStructuredSelector>

As of Reselect 5.1.0, you can create a "pre-typed" version of <InternalLinks.CreateStructuredSelector /> where the `state` type is predefined. This allows you to set the `state` type once, eliminating the need to specify it with every <InternalLinks.CreateStructuredSelector /> call.

To do this, you can call `createStructuredSelector.withTypes<StateType>()`:

{/* START: createStructuredSelector/withTypes.ts */}

<Tabs
  groupId='language'
  defaultValue='ts'
  values={[
    {label: 'TypeScript', value: 'ts'},
    {label: 'JavaScript', value: 'js'},
  ]}>
  <TabItem value='ts'>

```ts title="createStructuredSelector/withTypes.ts"
import { createStructuredSelector } from 'reselect'

export interface RootState {
  todos: { id: number; completed: boolean }[]
  alerts: { id: number; read: boolean }[]
}

export const createStructuredAppSelector =
  createStructuredSelector.withTypes<RootState>()

const structuredAppSelector = createStructuredAppSelector({
  // Type of `state` is set to `RootState`, no need to manually set the type
  // highlight-start
  todos: state => state.todos,
  // highlight-end
  alerts: state => state.alerts,
  todoById: (state, id: number) => state.todos[id]
})
```

  </TabItem>
  <TabItem value='js'>

```js title="createStructuredSelector/withTypes.js"
import { createStructuredSelector } from 'reselect'

export const createStructuredAppSelector = createStructuredSelector.withTypes()

const structuredAppSelector = createStructuredAppSelector({
  // Type of `state` is set to `RootState`, no need to manually set the type
  // highlight-start
  todos: state => state.todos,
  // highlight-end
  alerts: state => state.alerts,
  todoById: (state, id) => state.todos[id]
})
```

  </TabItem>
</Tabs>

{/* END: createStructuredSelector/withTypes.ts */}